Earlier this week, David Attenborough sat down to talk to BBC Newsnight ahead of his upcoming five-part nature series Dynasties, which will air on the BBC sometime soon. (The official release date has not yet been announced.) During the interview, the 92-year-old broadcasting veteran discussed the future of our planet, touching on plastic pollution, vegetarianism, population growth, and the Paris Agreement.

Attenborough's previous project, Blue Planet II, helped kickstart a global debate on our destructive addiction to plastic and the effect it is having on the world's oceans. (Not to mention the climate, wildlife, and our diets.) Speaking about single-use plastic bags in the wake of taxes and bans in several countries, Attenborough told Newsnight's Evan Davis: "We should do our best to avoid the use of plastic" but added, "one mustn't maximize the effect of not using a plastic bag."

"I think it's quite important in a democracy that people actually have something to do to express their concern and maybe plastic bags aren't the most important element in the whole plastic problem but it is something that people can do," said Attenborough.

"As well as the fundamentally important thing of course, which is to put in the politicians who actually recognize what the danger is and will do something that is difficult."

On vegetarianism, Attenborough admitted he's not a big carnivore but says there is no moral reason, biologically speaking, to steer clear of meat because we evolved to be omnivores. But that "[w]e have got to a stage in our own social evolution in which that's no longer practical because we simply can't destroy the natural forests and plains of the world to feed ourselves... We can't afford to do that so, therefore, we have to modify our diet."

It's not just our diet in need of a rethink. Attenborough says we have to slow down the "alarming" rate of population growth – and soon.

"In the long run, population growth has to come to an end," said Attenborough, highlighting that much of it comes down to people, like him, living for longer. While there is a strong case to make in saying that population growth will stabilize on its own accord, he thinks that when (and if) it does, the global population will already be too high for it to be sustainable.

He told Davis he's actually reassured by the changes in attitude around the world to our planet, sparked by the historic agreement, and the US leaving it won't stop that.

"There's a groundswell internationally of recognizing what we are doing to the planet and the disaster that awaits unless we do something," he said.

"To what extent the United States is going to withdraw from it, we'll see. My suspicion is that people will realize that, actually, the United States' attitude is outdated, it doesn't apply anymore, and I think that will be overcome."